Electric discharge system



Sept. 12, 1939.

c. J. R. H. VON WEDEL 2,172,631

ELECTRIC DISCHARGE SYSTEM Original Filed July 51, 1935 2 Sheets-Sheet 1.

[1V VENTQOR Carl J van Wade] Y Z ATTOMVEY Sept. 12, 1939- c; J. R. H.VON WEDEL 2,172,631

ELECTRIC DISCHARGE SYSTEM OriginalTiied July 51, 1935 2 Sheets-Sheet 2Patented Sept. 12, 1939 UNITED STATES,

2,172,031 rmc'rmc mscnancs srs'rmu Carl J. n. n. von Wedel, West Orange,N. 1., as-

signor to Thomas A. Edisom Incorporated, West Orange, N. .L,acorporation of New Jersey Application July 31, 1935. Serial 'No.33,967,

v Renewed January 18, 1939 12 Claims.

This invention relates to electric discharge systems, and moreparticularly to systems wherein the discharge takes place in a gaseousatmosphere. Throughout the specification the term gaseous has beenemployed as an adjective to denote either a gas or a vapor or acombination of gases and/orvapors, while the terms gas and vapor haveeach been used in a more specific sense. While not in all aspectslimited thereto, the invention has special reference to dischargesystems and devices for operation on-aiternating current.

An important objects of the invention is the provision of a gaseousdischarge device. or lamp for emitting ultra-violet radiations,particularly those of the so-called Dorno spectrum of wavelengthsbetween 2900 and 3100 Angstrom units,

capable of being inserted in an ordinary commer-.

cial powersupply socket and of. being operated proved self-containedgaseous discharge device arranged for starting and operating whenconnected directly with a commercial supply socket 215 without auxiliaryapparatus.

Another object is'the provision of a discharge system employing noveland useful mechanical and electrical arrangements of ballasting means.

Another object is the provision of an improved mutual circuitarrangement of ballasting means and cathode heating means. k

Another object is the provision of a simplified circuit arrangement forthe cathode heating means.

Another object is the provision of simple and improved means forautomatically starting he discharge.

Another object is the provision of simplified mutual circuitarrangements cf'the discharge v with the two contact elements of theEdison starting means and other portions of the system.

Still another object is the provision of an improved anode and mutualarrangement of anodes for a gaseous discharge device. o v. Still anotherobject is the provision of ballast-.- ing means capable of dispositionand operation within the gaseous atmosphere of a discharge device andadjacent lts'discharge column, and 0 methods of preparing the same.

a metal vapor discharge device.

Other and allied objects will more fully appear from the followingdescription and the appended sun another object is the provision ofsimple means for controlling the potential gradient of hereinafter setforth reference is had to the accompanying drawings, of which: Figure 1is a view in vertical cross-section 0 one form of discharge systemaccording to my invention; s

Figure 2 is an enlarged view of the electrode 5 of Figure 1 in morecomplete section;

Figure3 is a perspective view of one of the anodes of the device ofFigure l, in inverted posi-' tion; Figures 4 and 5 are horizontalcross-sectional views'respectively taken alc'ng lines 4-4 and 5-50fFlgurel;- v

Figured is a view generally similar to Figure 1, but illustrating asecond formof discharge system according to my invention;

Figure -7 is a horizontal cross-sectional view taken along the line 1-1of Figure 6;

Figure 8 is a vlew generally similar to Figures 1 and 6 but illustratinga third form of discharge 20 system according to my invention; and

Figure 9 is a simplified schematic view of the system of Figure 8. p

Reference is first directed to Figure 1. Herein appears the elongatedglass envelope I, which 25 for purposes of light emission in theultra-violet and particularly the Demo spectrum may be of "Uviol orCorex D" or equivalent glass. At the respective extremities of theenvelope two stems, 2 and 3, are sealed to form anair-tight enclosure;30 this is evacuated of air and contains a filling of vrare gas or a.rare gas mixture, for example ar- I gon and/or krypton, at a pressureofa few mm. ligand 9. source 4 of metal vapor-Jar example a globule ofmercury-shown clinging to. the walls 8 in the lower section of the tube.The stem 3 carries the electrode 5 including the cathode 6, all ashereinafter described. The stem 2 carries two lead-in wires 20 and 2|,respectively connected screw base 31 secured to the outside ofthe-envelope extremity adjacent stem 2; these wires as they passinwardly fromthe stem are shielded in any suitable manner, as by glasstubings 24, which may for example be integral withthe stem 2. On 4i'erred anode, however, I have illustrated in Figm 1 (and-in the detailFigure. 3' and sectional face 25' and the flange surface 25" at an acuteangle ,(for example 60 degrees) to each other. A suitably bent wire 23may be welded, within the acute angle, to the rear face of the flangesurface25 and to the outer extremity of the rear face of the activesurface 25' ,(this outer ex-. tremity being conveniently slightly angledwith respect to the main surface 25), and the wire 23 may be welded ontothe respective lead-in wire 20 or 2 I. This support of the anodes is socarried out that the flange surfaces 25" and 26' of the two respectiveanodes are parallel with each other and spaced apart a distance of theorder of the electronic mean free path in the gaseous atmosphere withinthe device, and that the active surfaces 25' and 26 each face some 30degrees outwardly from a line to the electrode 5 axial of the envelopeand are very thoroughly shielded from each other by the flange surfaces.The effect of this arrangement and of its individual features is so toshield the fields of the anodes as to reduce the danger of substantialionic cross currents, which lead to rapid disintegration and undesiredheating of the anodes and cross-arcing therebetween; to increase thelength of possible anodeto -anode discharge paths, reducing danger ofcross-arcing; and, by the flange surfaces and generally large ratio ofsurface to volume, to increase the cooling and decrease the operatingtemperature of the anodes, further reducing dangerof cross-arcing.

While carbon anodes, of other structure, may

be used and have been illustrated in later figures,

I prefer the metallic anodes-particularly those having metallic surfacessufficiently refractory to withstand the operating temperatures andcharacterized by oxyacids not more electro-negative than that ofmolybdenum. This is because these materials disintegrating from thesesurfaces, and transported toward and succeeding in landing onthe cathodeelement surface, do not significantly impair the operation of thecathode element orof the device as a whole-while in the case of carbonanodes, disintegrating material reaching the cathode element surfacereduces the effective area of that surface and causes carbon monoxidegas to contaminate the atmosphere within the device, and this causes anincrease of potential gradient and unstable and undependable operationof the device. Metals of the iron group and molybdenum, or alloys orplatings thereof, have been found satisfactory for the anodes of Figure1, depending on the supply voltage. To assist in reducing danger ofcross-arcing the surface of the anodes is preferably arranged to have ashigh a cathode drop as possible; the

cathode drop'of the metallic surfaces may be increased to some extent byoxidizing the surface, provided the anode temperature in the degassingoperation can be made substantially higher than thefnormal operatingtemperature but without decomposing the oxide. The dark color of theoxidized surface also increases heat radiation and causes relativelycooler operation of the anodes. An oxidized molybdenum surface issatisfactory as it will not decompose or dissociate even withyellow-white temperatures. A method of providing the high work functionoxidized surface, alternative to oxidizing the anode metal itself, is tocoat the same with a thin layer of a'refractory metallic oxide compound.

On the stem 3 is mounted an electrode 5, comprising a cathode elementand hea ng me ns therefor; the envelope I may conveniently be providedwith a widened portion la about this electrode 5. The cathode elementappears in Figure 1 as the generally helically ,formed heavy wire. 6;this wire is preferably provided with a corrugated or pitted surface(provided for example by welding or plating therearound a relativelyfine wire spiral) and is coated with an emissive oxide coating of theWehnelt type. The upper extremity of the ,helically formed wire 6 isdesignated as 6'; the helix is preferably formed with a progressivelyreducing diameter in its lower portion, from which leads downwardly thelower wire extremity 6".- Reference may now be had .for further detailsof -the electrode 5 to the enlarged, partly sectional Figure 2, whereinthe lorefractory insulating material, bf such material for example asthat of which the cylinder 1 is formed. Against the ends of the cylinder1 are "BI, 32. Over the heater winding 8 is preferably coated (as byspraying) and dried a layer 3' of fitted the circular nickel or othermetal end members I3, as by means of bosses I3 extending slightlyinwardly of the cylinder. These end members are provided with centralapertures III, the cathode element extremity 6" passing outwardlythrough this aperture in the lower end member l3 through an insulatingbushing II; in the upper end member I3 the aperture It serves to admitthe discharge to the cathode element 6. Co-axially surrounding theheater coil in spaced relation thereto is provided the cylindricalnickel or other metal shield can 9; this at its extremities is welded,to form a metallic enclosure for the heater coil 3, to end members [3,which are therefor made of appropriate diameter and peripherallyflanged. The cathode element extremity 6 is electrically connected tothe shield can 9 by welding to the upper end member l3; and the heatercenter-tap 8c is also connected to the can 3, as by welding directlythereto. The heater extremities, 3a and 8b, are led outwardly of theheater enclosure through the respective end members l3 in small tubes H,which may beof similar refractory insulating material to the cylinder I,and are electrically connected with wires l4 and I5 which are anchoredin stem 3. vFor further support of the electrode 5, and for de-gassmgpurposes as hereinafter mentioned, the cathode element extremity 6" maybe welded to a lead-in wire 19 passing outwardly of the envelope throughnected to the respective anodes through quite similar resistiveballasting and voltage dividing means, 28 and 29 respectively. Indifferent embodiments of my-invention these ballasting and voltagedividing means have taken different the lead-in wire I6 forms anddifferent physical dispositions; in all forms however it is desirablethat they have a high positive resistance coemcient with respect totemperature, and accordingly a suitable material for the resistanceelement proper thereof is tungsten wire, because of its increase ofresistance to some 10 times normal upon heating to temperatures of theorder of.1400 degrees centigrade.

'The baliasting means of Figure 1 are disposed within the envelope l,and. may be in the form of thin spirals 21 of the resistance wireimbedded (in rods or tubings 2|r (hereinafter referred to simply asrods) of refractory insulating material such as Steatite. While I intendthereby no limitation of my invention thereto, I may fluoride and thelike.

, and the coating in turn sintered. I prefer, however, to make thewindings upon the rods with the latter in semi-plastic or hardened butunsintered form, thereupon to apply the coating of similar material overthe winding and finally to heat or sinter the entire assembly as a unit.

' This serves to render quite homogeneous the material under, over andaround the winding, reducing possible tendencies toward chipping off ofthe coatings. Another method of construction of such units as theresistive ballasting means .of Figure 1, available for securing thoroughhomogeneity of the material, is the extrusion of a rod of thematerial-the winding, al-

ready formed as a spiral,being coincidentally fed centrally out of theextruding aperture; and the extruded unit being thereafter sintered.

In Figure 1 the ballasting means 28 and 29 have each been divided intotwo portions, each portion comprising a rod 211' having wire 21 imbeddedtherein: 28 into the upper and lower portions 28a. and 28b respectively,joined by the metallic sleeve 30; and 23 into the upper and lowerportions 29a and 231) respectively, joined by the metallic sleeve 3|.The ballasting means 28 has been provided with bottom and top caps 32and 34 respectively, and the ballasting means 29 with the bottom and topcaps 33 and 35 respectively. The bottom caps 32-33 and sleeves 30-3lhold the respective rod extremities firmly;

while the top caps 34-35 are made of slightly larger internal diameterso that rods may ex- -pand or contract longitudinally by severalmillihowever, obtained good results with metals of.

the iron group such as nickel by spraying the surface, to provide forless-emissivity'and better radiation, with a compound of the nature ofSteatite and capable of sintering at the temperatures employed indegassing of the device. Similar material may be used to sinter thesleeves 30-3| and the caps 32-33 to the rods 2'lr-a convenient method ofsecuring solid connections being toprovide in the sleeve or cap slots(such as 30" in sleeve 30) and to spray the compound into the slots, andanother method being to pre groove' the sleeve or cap and turn it ontothe.

tubing. The extremities of the wires 21 in the two rods 2'|r terminatingwithin sleeve 30 or 3| are jointly brought outwardly through the sleeveand welded to the outside, as at 3|; the extremity of the wire 21 in therod-terminating in any of the caps 32-33-3445 is brought out through theend portion of the'cap (which is originally in tubing form)v and the endportion then pinched together to hold and connect with the ,wire. Thecaps 34 and 35 may be welded to the outer extremities of the respectiveanode surfaces 25' and 26', and the caps 32 and 33 to the topextremities of the respective wires 14- and I5, which are oppositelyspaced about the envelope axis in alignment with the outer anodeextremities, and slightly 'anodeward from theshield can 9.

The ballasting means 28 and 29, being within the envelope I and having aporous surface containing a large quantity of foreign gas, must beheated to high temperature in the de-ga'ssing operation performed on thewhole device; this heating must penetrate the whole length of the rods211, including the'portions in contact with the means and the electrode5. To facilitate decurrent entering them as anodes; as will here- Iinafter be apparent, however, their potentials relative to thepotentials of other elements within the envelope l are. such as torender them capable of undesired action; as cathodes. Ac-

cordingly they must be of such material and surface as to obviate anyemissivity atthe tem-' peratures they will attain; the surface should Itherefore be of good heat-radiating properties and of high workfunction. surfaced-oxidized molybdenum maybe satisfactorily employed; Ihave,

gassing of the latter and more thoroughly to heat and de-gas the cathodeelement 8, current may be supplied to the cathode element through themedium of lead-in wires, I 6 and I9 which are available externally ofthe device. After the degassing, of "course, the rare gas filling andthe vaporizable metal (i. e. mercury) is inserted in the device.

The structure of the device of Figure 1 having been thus described,attention may be directed to the manner of its operation, in connectionwith which will be mentioned certain typical parameters; itwill beunderstood, however, that these parameters are set forth in anillustrative and strictly non-limitative sense.

The ,device may be considered as adapted for normal operation oncommercial alternating cuent supplies of the usual voltage of or volts,being adapted for connection with a standard light socket by means ofthe base 31. When the supply is connected, it will be obvious that theanodes are immediately established at an alternating potentialdiilerence coinciding with that of the supply-say 113 volts R. M. S.-and

lishes the cathode-element. and the shield can 9 4 (which are connectedto the heater center-tap to) at a uniform mid-potential; exemplarily56.5

volts R. M. S. from each anode. By the current flow through the heaterwinding 2 the cathode is heated, and after an interval becomes emissive.

It will be seen that throughout this heating in tervalthe bottom caps 32and 32 are {at alternating potentials diilerent from that of the cathodeelement 6 by'the alternating voltage drop in hall the heater winding,and hence are made alternately positive with respect-to the cathodeelement by the peak value of this voltage drop. This peak voltage drop.is made somewhat higher than the ionization potential of the rare gasfilling, by suitable-apportionment of the resistance values oi theballasting means and heater. Ac-

cordingly when the cathode becomes emissive the mentioned potentials onthe bottom caps, which are verynear the aperture Ill in the top shieldend member l3, will introduce ionization of the gaseous filling and adischarge between the bottom caps alternately and the cathode element.It may here be mentioned that while the bottom caps have just beendescribed as efiecting this action and are suitably positioned therefor,it

may be.p'referable to connect to each a starting electrode plate whichmay be disposed a little nearer the axis of the envelope and thus in astill more iavorable position with respect to the aperture III toeflect'this action. Such starting electrodes I have illustrated inFigure l as l1 and I8, respectively supported on and connected to thebottom caps 32 and 33 by the wires i1 and I8. Current flow attendant onthe discharge just mentioned will of course be limited by both theballasting means; but the ions created by the discharge difluse to thenearby walls 0! the envelope I, strongly reducing the negativeelectronic charges on the envelope walls in the lower envelope portion.

' Attention is now directed to the sleeves 30 and M, which are atalternating potentials diflerent from that of the cathode element S by'the alternating drop in half the heater winding plus the alternatingdrop in one of the mutually similar lower ballast portions 28b, 29b, andhence ,are

alternating positive with respect to the cathode element by a peakvoltage considerably exceeding I anodes 25, 26, becomes effective toextend the discharge throughout the length of the device. Thus by aseries of anodic elements at progressive distances from the cathodeelement and at pro-,

gressively increasing potential diflerences therefrom I am able toinitiate the main arc discharge without resorting to high voltageinductive kicks or high frequency ionizations to overcome the fields 0the electronic wall charges.

The anodes 25 and 26 are of course alternately positive. Considering onehalf-cycle during the main discharge beginning at an instant when bothanodes coincide in potential with that of the cathode element (which maybe taken as 9. reference potential), the instantaneous anode 25potential will begin to rise and the instantaneous anode 26 potentialcorrespondingly to .fall. When the'anode has reached an instaneouspositive potential corresponding to the bi-cyclic starting voltage dropin the discharge'column (which will be at least slightly greater thanthe potential gradient as measured over the predominate portion of thehalf-cycle), the discharge from it to the cathode element comes intoplay and prevents its further potential rise relative to the cathodeelement. The cathode element potential thereupon diverges positivelyfrom the mid-potential oi the supplyor, relative to the cathodepotential, the anode 26 potential continues its negative increase at ahigher rate to the peak of the-halfcycle, when it will be of a negativevalue equal to the peak supply voltage less onlythe potential gradientof the column. In the declining hall of the half-cycle the negativepotential of the anode 26 decreases at the higher rate, and the positivepotential of anode 25 remains constant at the value of the potentialgradient, until late in the half-cycle when the positive and negativeanode potentials again become symmetrical about the cathode elementpotential and together fall from the value of the predominate potentialgradient to zero at the normal rate, the discharge extinguishing. In thenext half-cycle the action of course is repeated, but with the anodesinterchanged; and so on.

When the main discharge is first initiated the potential gradient in.the discharge column is relatively low, being determined essentially bythe rare gas filling and being typically of the order 0122 to 25 volts.The current and power in the device, being limited by the ballast meansconnected to the momentarily more negative anode and beingquantitatively the quotient of the potential of this anode (relative tothe oathode element) by the resistance of this ballast means, is nowconsiderablyincreased over that obtaining during the heating period.This increase, however, is represented almost exactly by v I power inthe discharge column; the R, M. S. or heating value of the current (andhence the average power) in the two ballast means and heater halves,taken over a whole cycle, has not materially changed-Jar whilethe'voltage across and current through one ballast means andhalfheaterhave been materially increased in one halfcycle, they have beensubstantially correspondingly reduced in the next half-cycle by theshunting action of the discharge. The heat inertia of the ballast meansis sufliciently high so that, while the ballast temperature andresistance may yet respond quite rapidly to appreciable R. M. S.

current changes, they do not significantly change with theseintra-cycllc variations.

As the main discharge continues the device and its envelope I are beingheated up by the ballasting means, heater and discharge column, and thevapor density and pressure are rising. After a short interval the vapordensity will have risen to the order of the 'gas density and the wholedischarge current will be carried by the vapor ions, which have a lowerionization potential than the rare gas. As the vapor density yetcontinues to rise the potential gradient will increase, with increasingtemperature of the device, until at some temperature the device willstabilize by radiating the same amount of energy as is being supplied toit. At this point the efiective or R. M. S. voltage across the dischargecolumn may have increased for example to the order of 31 to 36 volts(roughly the equivalent of 35 to 40 volts potential gradient as measured.*'er the predominate portion '0': each half-cycle) Under theseconditions the currents through either ballast means and associatedhalf-heater in successive half cycles will obviously vary slightly less,

between those half-cycles. than in the early period of the main arcdischarge.

While after the discharge has re-started each I half-cycle anessentially constant or predominate potential gradient persists untildischarge extinguishment late in that half-cycle, the re-startinggradient or requisite potential for re-starting in each successivehalf-cycle is somewhat in excess of this predominate gradient value. Itis very essential that the cooling facilities of the device he soarranged that the stabilization of temperature and vapor pressure of thedevice occur at a point where the predominate potentialgradient will beonly a fraction of half the peak supply voltage, so' that an amplemargin will be provided for this excess, for line voltage fluctuations,for the-reduction of stroboscopic effects, and for stability generally.Of course the vapor pressure p is determined by the coldest spot ofthe-wall of envelope I, which may be the bottom portion of the envelope,and it-is largely the cooling facility of this section which determinesthe vapor pressure. Accordingly I may place about the lower end of theenvelope, adjacent this section, a

thimble 36; by choice of the material of this thirnble between dark orlight metal or insulating material such as Bakelite I may control tosome extent the radiation from and cooling facility of this section andhence the vapor pressure and potential gradients. In other words, thesame type of device may be used indifferent supply voltages and adjustedto proper operation by changing this thimble.

Assuming the device to be adjusted for.40 volt, predominate potentialgradient, and to be provided with ballast means and heater winding suchthat the normal hot resistance of each ballast and associatedhalf-heater is of the order of 38 ohms,

the device on 113 volts supply will draw approximately 2.1amperes R. M.S., the R. M. S; current" through any portion of the ballast-heatersystem over a whole cycle will be of the order of 1.6 amperes, theaverage current through the discharge column of the order of .9 ampere,and the power consumptions in the'ballast-heater system and in thedischarge column may be of theorder of 200 and 36 watts respectively.While it is true that the energy in the luminous column represents onlya little over 15% of the total energy expended, it is to be borne inmind that this efficiency is a minor factor compared with simplicity,capability of complete self-contained nature, and operation in stahdardsockets and without the air of experts-particularly for such specialpurposes as a health lamp. In the example cited, with-a discharge columnlength of the order of 15 to 18 centimeters, the emission from'therather dense vapor through the Uviol or Corex D glass contains a veryconsiderable ultra violet radiation-from which by the filter action ofthe glass is quite sharply excluded the undesirable shorter wavelengthradiations below the,2900 Angstrom unit lower limit of the Demofspectrum.

By the same token that considerable power is expended in the ballastingmeans, these means are of such relative magnitude as to,result inexcellent uniformity and stability for the system in the face of supplyvoltage variations-provided of course that'the predominate potentialgradient of the discharge column is made a reasonable one as abovediscussed. This effect is assured not merely by the magnitude of theballasting means but also by their high resistance-temperature co,efficient, for on supply voltage fluctuations they change theirresistance and tend to maintain a constant discharge column current andenergy. The uniformity of operation of the device in the face oftemperature changes, whether produced internally or .externally of thedevice, is also good-for while the column will change its potentialgradient with temperature changes, a

Furthermore, in view of the voltage-dividing ac-.

tion of the ballasting means with resulting shunting of alternateportions by the discharge column, the natural increase of'currentthrough one portion of the ballasting means by the discharge in any onehalf-cycle is compensated for by a reduction in currentthrough the otherportion, so that the R. M. S. current through any one portion of theballasting means overa whole cycle is maintained substantiallyunincreased upon initiation of the discharge; accordingly the heater, inseries with theballasting means"2829 and thus effectively forming aportion of the total ballasting means,.is not overheated during themain" dischage. The preferred division of the heater into halvesrespectively connected in the two portions of the voltage divider systemresults under all conditions in symmetry of the currents and dischargecharacteristics in successive half cycles,

which might otherwise be upset bydiiferent ther-- mal inertiae of theheaterand ballasting means and possibly difierent resistance-temperaturec0- efilcients. Furthermore the heater by virtue of this symmetricaldivision may be=availed of as the voltage dividing means for'establishing suitable symmetrical initial starting potentials.

The resistance of each ballast means and halfheater-above mentioned astypically about 38 ohms in normal hot condition for a device with theexemplary 'parameters abovementiondshould be suitably apportionedbetween" the ballast means portions (e. g. 28a, 28b) and the halfheaterto provide useful yoltages for the initial starting electrodes (e; g.,l1, l8) and the intermediate starting electrodes (e. g 30, 3|). Hotresistances very approximately in the ratios of 312:3 for the ballastportion 2811 (or 290.), ballast portion'28b (or 29b) and half-heater 81(or 82) respectively may be found useful; it is to be noted, however,that the cold resistances may be in somewhat different ratio (i.'e.,that of each halfheater relatively less) in view of a somewhat greatertemperature attained in operation by the heater than by the ballastingmeans 28 and 29.

The latter temperature is preferably maintained not too great-forexample it may be maintained under operating conditions around 1000degrees centigrade and not above 1400 degrees centigrade. In a device ofthe approximate operating parameters exemplarily set forth above'I haveemployed, for the material of the resistance element 21 of theballasting meansftungsten wire as used for commercial 300 wattincandescent -120 volt lamps-but with the difference that the spiralshave been made of greaterdiameter and larger pitch. In the structure ofFigure 1 theresistance elements 21 of the ballasting means are imbeddedin the rods 211" to shield them effectively from the discharge, forotherwise ionic bombardment of the element would lead to disintegration,and the heated elements would cause cross-arcing within the tube; theballasting means are spaced sufficiently on opposite sides of theenvelope axis to avoid serious effect on the potential gradient pi thedischarge column. In FiguresG and 'l I illustrate a modified form of thedevice wherein-the most essential change is .the protection of theresistance elements 21 of the several ballasting means portions by theirenclosure in sealed glass tubes to form lamps (44a, 44b, 45a and 45b) ofthe order for example of 12 millimeter diameter, which are evacuated andpreferably filled with an inert gas of about atmosphere pressuresimilarly to ordinary gas filled lamps. It is essential that theballasting I means remain sufilciently spaced away from the envelopeaxis to avoid seriously raising the potential gradient of the dischargecolumn, and in .view of their increased diameter it is necessary towiden the envelope l throughout most of its length. Accordingly it mayconveniently be provided with the central portion I (opposite thedischarge column) of flattened or approximately ellipticalcross-section, the lamps being located roughly in thefoci of theapproximate ellipse as appears in the sectional Figure 7; this avoidsthe somewhat undesirable large cross-section of the discharge path werethere employed simply a circular envelope cross-section of largerdiameter.

In Figure 6 by way of alternative illustration I have shown cylindricalcarbon anodes 4i and 42 supported on the lead-in wires 2I'and 2| (withwires 53 and 54 also supported on these lead-in wires and extendingoutwardly to support and connect to the upper ballast means a and s)These anodes may be shielded from each other. for minimization ofdisintegration and cross-arcing propensities with higher supplyyoltage's, by the conductive or insulating shield l3 interposed 5therebetween and supported in a wire 43' sealed in the stem 2.

In order to provide intermediately active starting electrodes analogousto the sleeves 30 and SI of Figure 1. I may again divide each ballastinmeans into upper and lower portions comprisin lamps a and brespectively, and a and lib,

respectively. These portions may be joined by wire 48 on the one handand wire ll on the other,

and intermediate starting electrode plates ll and 41 supported andconnected to these respective wires by wires 46 and 41'. To retain thejunctions of upper and lower lamps against transverse movement wirespiders 50 and 5! may be secured to the wires I} and ll, and led, aroundand biased against the interior wall of the envelope section I' intomechanical connection with each other- "which connection is howeverinsulated by blocks 52 of insulating material to avoid short-circuitlngthe wires 48 and ll.

I have found that in'devices of medium length (e. g., of about 15centimeters discharge column) the main discharge can be introduced eventhough the intermediate starting electrodes (e. g., sleeves ill and llor electrodes 46 and 41) are omitted and.

each of the two ballasting means made in one integral part. isparticularly the case when, as especially true of the lamps of Figure 6,the.

cooling period of the ballasting means .is small compared to that of theelectrode 5 and heater winding ltherein. For in this case one canconnect the supply for a sumcient interval to heat the cathode elementto emissivity and develop a 6 discharge to the initial startingelectrodes (e. g., ll, l8), interrupt the supply for a few seconds topermit the ballasting means to cool, and again connect the supply. Onthis second connection the main discharge will dependably start for the10 charge path toward the main anodes and permitting the main dischargeto strike therefrom.

With the omission of the intermediate starting 25 electrodes it becomespossible to arrange the ballasting means outside the envelope l;.atypical such arrangement I have illustrated structurally in Figure 8 andschematically in Figure 9. Before referring more detailedly to thesefigures, I 30 may mention that in each of the ballasting means in thesefigures I have shown an inductance. It will be understood thatthispartial use of inductive ballasting means is optional; its generaladvantages are the permissible reduction of 35 pure resistance value ofthe ballasting means resulting in lowered power consumption andincreased power efilciency, and slight prolongation of the discharge ineach half cycle resulting in increased stability and/,or the abilitydependably 40 to operate the discharge column at a somewhat higherpotential gradient; its disadvantages are obviously somewhat increasedcost, and an impairment of power factor to a degree generallycorresponding to the degree of power efilciency 5 increase. Wheninductance is employed, I prefer so to limit its value as to maintain apower factor of the order of '75 or 80%. It will be un-' derstood, ofcourse, that the inclusion of the inductive ballast portions does notalter the basic 50 action of the system, nor impair its most funda- Imental advantages.

In Figure 8 the device I may be generally similar-to that of Figure 1,excepting that the ballasting means ila, 28b, 29a, 291) (with theintermediate starting electrode means) are omitted from within thedevice, and merely by way of iilustration, the anode structure of Figure6 has been employed. The Edison base 31 of the device has been shownscrewed into the inverted so socket 38; this is secured in the center ofa downwardly directed reflector ll. On either side of the socket 30 arealso secured to .the reflector the inverted sockets I2 and 83; intothese sockets are screwed the resistive ballasting means and 5 ii in thephysical form of evacuated or gasfilled light bulbs having as theirfilaments the necessary ballast resistance wire 21. Over thebottom'extremity of the device I is secured the I Bakelite or'other capll carrying terminals i4 7 minals 62 and 83 of sockets 62 and 63. Theother terminals of these sockets are connected by respective conductors64 and G to respective inductance coils 65 and 61, and therethrough (atvpoints 20" and 2| to the respective leads 20' is employed it isdesirable to arrange the coils,

electrically in that mutual phase relationship, readily determined bytest, which yields the more stable system operation tendenciesresultingfrom the mutual coupling 0! the coilsthrough the common core.

The core elements or common core may be se- I cured to the top of thereflector III as by bracket 69. Above the coils may be provided theinvertecl pan-shaped member ll secured around-its periphery tothe top ofreflector Ill and thus enclosing the coils. On the top of this member Hmay be secured the Edison base 12 having relatively insulated shell 12aand tip contact 12b to which the leads 20 and 2| are respectivelyconnected. By means of this base 12 the .entire assembly may be screwedinto any available commercial supply line socket, forming a convenientarrangement in which the device I and lamps 60 and ii are each readilyreplaceable by the layman-at any terminationof their useful life.

ments of the bulb lamps 60 and BI of Figure 8, or the tubular lamps 44a,bJSa, 45b of Figure 6,

' may be apportioned to operateat temperatures the heater winding wasnot center-tapped. As

pointed out in that application, the spacing between the can 9 and theheater 8 should be made of the order of the mean free path length ofelectrons in the gaseousfilling within the can at operatingtemperatures, in order to minimize danger of cross-arcing between canand heater or between portions of the heater. Also, as pointed out inthat and a prior co-pending application invconnection with a helicalcathode element of the type or '6 herein, the internal diameter of thehelix should be made several times the mean free path length ofelectrons in the gaseous filling within' the cathode enclosure atoperating temperatures, so that there may develop within and not outsidethe enclosure an ion cloud or region'of intense positive ionization. Itwill of course be appreciated that in the instant invention other formsof cathode than the helical element 6 may be employed, but preferablywhen a cathode enclosure is provided the ion cloud will be maintainedwithin the enclosure.

It may further be particularly mentioned, in connection with the heaterwinding 8 which I cylinder"! in a similar manner to that which I havedisclosed tor-the preparation 01% resistance It will of course beunderstood that the fila- 7 rods 211-. That a to say, the winding I isprete ably made on a cylinder or tube 1 which is semiplastic or hardenedbut not yet slnteredrthe coating 8' of similar material to the cylinder1- is sprayed or otherwise coated over the winding, and the wound andcoated cylinder is then heated M and sintered as a unit; thus thewinding 8 becomes imbedded in a homogeneous mass relatively free ofstrains-which might later tend to cause the-coating 8' to crack ofl.

It has been most convenient in the description to refer by the termballasting means to the elements shown as connected from the heaterextremities to the anodes. however, that the heater and itsrespective'halves are likewise portions of the actual ballast; and theterm ballasting means" and the like, being employed in the claims in abroad context, will therein be understood to include within its scopethe heater and its halves. I I

It will be appreciated,

I do not intend that the scope of my invention be limitedby the detailsof the particular embodiments and structures shown and described, as itwill be obvious that these may be modified without departure ,i'rom thespirit of the invention. :And it is my intention to claim herein, asbroadly as the state of the art will permit, ail the various 'novelcombinations, sub-combinations and features herein disclosed,

I claim; I

1. In combination in an electric discharge system: a source ofalternating current; ballasting means connected across said source; anda gaseous discharge device including a thermionic cathode electricallyconnected to a point of intermediate potential in said ballasting means,two anodes electrically connected to points in said ballasting means oirespectively opposite potential difference from, said cathode, andstarting electrode means disposed near said cathode and electricallyconnected to at least one point of intermediate potential in saidballasting means.

2. In combination in 'an electric'discharge systemi a source ofalternating current; ballasting means connected across said source; anda gaseous discharge device including a thermionic cathode electricallyconnected to a point 01' inter mediate potential in said ballastingmeans, two anodes electrically connected to points in said ballastingmeans of respectively opposite potential difierence from said cathode,and a plurality of starting electrode'means in progressive spacing fromsaid cathode toward said anodes and respectively connected to points insaid ballasting means of progressive potential diflerences from saidcathode. J 3. In combination in an electric discharge system: a gaseousdischarge device comprising a gaseous filling, a heater winding; athermionic cathode adjacent and influenced by said heater winding andconnected to a point thereon, and two anodes adapted for connectionacross an alternating current supply; two ballasting means eachconnected from a respective one of said anodes to a respective extremityof saidwinding, of such magnitude as to cause a voltage drop, betweensaid winding point and at least one of said winding extremities, inexcess of the ioniza-r tion potential of said gaseous filling; ,andstarting electrode means adjacent said cathode and electricallyconnected to at least said one winding extremity.

4. In combination in a gaseous discharge device: an elongated envelopeand .therewithin a gaseous filling, a cathode near one envelope ex- 15tremity, and two anodes near the other envelope extremity and adapted tohave impressed therebetween an alternating voltage and to support adischarge alternatingly to said cathode: said anodes being of refractorymetal, having flanges mutually parallel and spaced apart a distance ofthe order. of the mean free path length of electrons in said gaseous.filling at operating temperatures, and each anode having adischarge-supporting surface bent outwardly from its said flange andfacing in a direction outwardly divergent from the direction of saidcathode.

5. In combination in a gaseous discharge device: a cathode, and twoanodes relatively spaced from said cathode and adapted to have impressedtherebetween an alternating voltage, said anodes being of refractorymetal, each having flange and active surfaces at an acute angle relativeto each other, and being mutually arranged with their said flangesurfaces parallel and closely spaced and with said angles pointing Itoward said cathode.

6. In combination in an electric discharge sys- -tem: a gaseousdischarge device comprising a heater winding, a thermionic cathodeadjacent and influenced by said winding and connected to a pointthereon, and two anodes adapted for connection across an alternatingcurrent supply; two ballasting means each connected from a respectiveone of said anodes to a respective extremity of said winding; andstarting electrode means within said device adjacent said cathode ply;two ballasting means each connected froma respective one of said anodesto a respective extremity of said winding; and starting electrode meanswithin-said device adjacent said cathode and electrically connected tointermediate points in said ballasting means.

v8. In combination in'a gaseous discharge de-'-. vice: an elongatedenvelope; two anodes adapted for connection to an alternating currentsupply,

disposed within said envelope near one extremity thereof; a thermioniccathode disposed within said envelope near the other extremity thereofand adapted to receive a discharge from said anodes; a heater windingdisposed in heating relationship to said cathode and intermediatelyconnected thereto; two resistance elements disposed within said deviceand each electrically connected from a respective extremity of saidwinding to a respective said anode; and" starting electrode meansconnected with at least one of said resistance elements remotely fromeither of said anodes.

9. In a gaseous discharge device having an envelope and means, includingmain electrodes, for maintaining a discharge therewithin; two seriallyarranged resistances disposed within said envelope; insulating tubingsenclosing said resistances; and a metallic sleeve fitting about an endof each of said tublngs, electrically connected with an end oi each ofsaid resistances, and exposed to the space within said device for actionas'an auxiliary electrode. a

10. In combination in a gaseous discharge device: an elongated envelope,discharge-suDDQrting electrodes near respectively opposite extremitiesof said envelope, and two resistances extending longitudinally of saidenvelope therewithin, said envelope having a cross-section substantiallyin the form of an ellipse, and said resistances being disposedapproximately at the foci of said ellipse. 4

11. In combination in a gaseous discharge device: an elongated envelope,discharge-supporting electrodes near respectively opposite extremitiesof saidv envelope, and a resistance extending longitudinally of saidenvelope therewithin, said envelope having a cross-section substantiallyin the form of an ellipse, and said resistance being disposedapproximately at a focus of said ellipse.

envelope and means for supporting a discharge therewithin: ballastingmeans within said envelope for said discharge, and auxiliary startingelectrode means permanently connected to an intermediate point in saidballasting means.

CARL J.- R. H. von wnnnn v CERTIFICATE OF CORRECTION. Patent No.2,172,6 1. September 12, 19 9.

CARL J. R. H.- von WEDEL.

It is hereby certified that error appears in the printed specificationof the above numbered patent requiring correction as follows: Page 1first I column, line 13, for the word "objects" read object; and secondcolumn, line 51;, for "anode" read anodes; page 5, second column, line52, for "Le." read e.g.; page L, second column, line 2, for "instaneous"z-ead instantaneous; page 5, first column, line 58, for "air" read aid;and second.

column, line 5?, for "dischage" read discharge; .page 8, second column,line 16, claim 9, after "therewithin" change the semicolon to a colon;

and that the said Letters Patent should be readwith this correctiontherein that the same may conform to the record of the case in thePatent Office.

Signed and sealed this lhth da of November, D 1959..

Henry Van Arsdale, (Seal) -Ac ting Commissioner of Patents.

